A patient with homozygous sickle cell disease presented with sickle crisis complicated by hepatic and pulmonary sequestration and required intensive therapy. During the recovery phrase she developed a rapid rise of haemoglobin concentration, unrelated to blood transfusion, followed by hypertension, congestive cardiac failure and catastrophic intracerebral haemorrhage. This serious haemodynamic disturbance was considered to be caused by a reversal of the sequestration process. Careful monitoring of a sickle cell patient's blood pressure, blood counts, haematocrits, haemoglobin S level and plasma viscocity, even after the end of a sequestration crisis, is recommended.